Methods of producing and polishing semiconductor device and polishing apparatus

ABSTRACT

A method of production and a method of polishing a semiconductor device and a polishing apparatus, capable of easily flattening an initial unevenness of a metal film, excellent in efficiency of removal of an excess metal film, and capable of suppressing damage to an interlayer insulation film below the metal film when flattening the metal film by polishing, the polishing method including the steps of interposing an electrolytic solution including a chelating agent between a cathode member and the copper film, applying a voltage between the cathode member used as a cathode and the copper film used as an anode to oxidize the surface of the copper film and forming a chelate film of the oxidized copper, selectively removing a projecting portion of the chelate film corresponding to the shape of the copper film to expose the projecting portion of the copper film at its surface, and repeating the above chelate film forming step and the above chelate film removing step until the projecting portion of the copper film is flattened.

This application is a divisional application of Ser. No. 09/800,580filed Mar. 8, 2001 now U.S. Pat. No. 6,797,623, issued on Sep. 28, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods and apparatus of producing andpolishing a semiconductor device, more particularly relates to methodsof producing and polishing a semiconductor device including a step ofreducing surface unevenness accompanying the formation of a metal film,and to a polishing apparatus thereof.

2. Description of the Related Art

Along with the increase in integration and reduction of size ofsemiconductor devices, progress has been made in miniaturization ofinterconnections, reduction of interconnection pitch, and superpositionof interconnections. The importance of the multilayer interconnectiontechnology in the manufacturing process of semiconductor devices istherefore rising.

Aluminum has been frequently used as an interconnection material of asemiconductor device having a multilayer interconnection structure, butin order to reduce the propagation delay of signals in the recent 0.25μm or less design rule, has been attempted active development of aninterconnection process in that aluminum as the interconnection materialis replaced by copper. When using copper for interconnections, it isbeneficial that both a low resistance and a high electromigrationtolerance can be obtained.

In a process using this copper for interconnections, for example, aninterconnection process referred to as the damascene process for buryinga metal in a groove-like interconnection pattern formed in an interlayerinsulation film in advance and removing excess metal film by chemicalmechanical (mechno-chemical) polishing (CMP) to form theinterconnections has become influential. The damascene process has thefeatures that etching of the interconnections become unnecessary andalso a further upper interlayer insulation film becomes flat by itself,so the manufacturing steps can be simplified.

Further, by the dual damascene process, where not only grooves for theinterconnections, but also the contact holes are formed as grooves inthe interlayer insulation film and where the interconnections and thecontact holes are simultaneously buried by the metal, a greaterreduction of the interconnection steps can be achieved.

Here, an explanation will be made of an example of the process forforming copper interconnections by the dual damascene process withreference to the accompanying drawings.

First, as shown in FIG. 25A, for example, an interlayer insulation film302 made of silicon oxide is formed by low pressure chemical vapordeposition (LP-CVD) on a silicon or other semiconductor substrate 301 onwhich a not illustrated impurity diffusion region is appropriatelyformed.

Next, as shown in FIG. 25B, contact holes CH communicating with theimpurity diffusion region of the semiconductor substrate 301 and groovesM in which it will be formed a predetermined pattern of interconnectionsto be electrically connected to the impurity diffusion region of thesubstrate 301 which are formed by using well-known photolithography andetching.

Next, as shown in FIG. 25C, a barrier film 305 is formed on the surfaceof the interlayer insulation film 302 and in the contact holes CH andthe grooves M. This barrier film 305 is formed by a material such as Ta,Ti, TaN, or TiN by well-known sputtering. When the interconnectionmaterial is copper and the interlayer insulation film 302 is siliconoxide, since copper has a large diffusion coefficient with respect tosilicon oxide, it is easily oxidized. The barrier film 305 is providedto prevent this.

Next, as shown in FIG. 25D, a seed copper film 306 is formed on thebarrier film 305 to a predetermined thickness by well-known sputterings.

Then, as shown in FIG. 25E, a copper film 307 is formed so as to burythe contact holes CH and the grooves M by copper. The copper film 307 isformed by the process of plating, CVD, sputtering, etc.

Next, as shown in FIG. 25F, the excess copper film 307 and barrier film305 on the interlayer insulation film 302 are removed by CMP forflattening.

Due to the above steps, copper interconnections 308 and contacts 309 areformed.

By repeating the above process on the interconnections 308, multilayerinterconnections can be formed.

Summarizing the disadvantages to be solved by the invention, in the stepof removing the excess copper film 307 by CMP in the copperinterconnection forming process using the dual damascene process,because the flattening technique employing conventional CMP involvesapplying a predetermined pressure between a polishing tool and thecopper film for polishing, it suffers from a large damage given to thesemiconductor substrate. Especially in a case where an organicinsulation film of a small dielectric constant having a low mechanicalstrength is adopted for the interlayer insulation film, this damage nolonger becomes negligible and may cause cracks of the interlayerinsulation film and separation of the interlayer insulation film fromthe semiconductor substrate.

Further, the removal performance differs among the interlayer insulationfilm 302, the copper film 307, and the barrier film 305, therefore itsuffers from the disadvantage that dishing, erosion (thinning),recesses, etc. easily occur in the interconnections 308.

Dishing is a phenomenon where, as shown in FIG. 26, when there is aninterconnection 308 having a width of for example about 100 μm at forexample a 0.18 μm design rule, the center portion of the interconnectionis excessively removed and sinks. If this dishing occurs, the sectionalarea of the interconnection 308 becomes insufficient. This causes poorinterconnection resistance etc. This dishing is apt to occur when copperor aluminum, which is relatively soft, is used as the interconnectionmaterial.

Erosion is a phenomenon where, as shown in FIG. 27, a portion having ahigh pattern density such as where interconnections with a width of 1.0μm are formed at a density of 50% in a range of for example 3000 μm isexcessively removed. When erosion occurs, the sectional area of theinterconnections becomes insufficient. This causes poor interconnectionresistance etc.

Recess is a phenomenon where, as shown in FIG. 28, the interconnection308 becomes lower in level at the interface between the interlayerinsulation film 302 and the interconnection 308 resulting in a stepdifference. In this case as well, the sectional area of theinterconnection becomes insufficient, causing poor interconnectionresistance etc.

Further, in the step of flattening and removing the excess copper film307 by CMP, it is necessary to efficiently remove the copper film. Theamount removed per unit time, that is, the polishing rate, is requiredto be for example more than 500 nm/mm.

In order to obtain this polishing rate, it is necessary to increase thepolishing pressure on the wafer. When the polishing pressure is raised,as shown in FIG. 29, a scratch SC and chemical damage CD are apt tooccur in the interconnection surface. In particular, they easily occurin the soft copper. For this reason, it causes opening of theinterconnections, short-circuiting, poor interconnection resistance, andother defects. Further, if the polishing pressure is raised, there isthe inconvenience that the amount of the scratches, separation ofinterlayer insulation film, dishing, erosion, and recesses also becomeslarger.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a method ofproducing a semiconductor device capable of easily flattening an initialunevenness, excellent in efficiency of removal of an excess metal film,and capable of suppressing damage to an interlayer insulation film belowa metal film when flattening the metal film by polishing; a secondobject of the present invention is to provide a method of polishing thesame semiconductor device; a third object of the present invention is toprovide a polishing apparatus using these methods.

An object of the present invention is to provide a method of productionand a method of polishing a semiconductor device capable of easilyflattening an initial unevenness, excellent in efficiency of removal ofan excess metal film, and capable of suppressing damage to an interlayerinsulation film below a metal film when flattening the metal film bypolishing and to a polishing apparatus used for these methods.

To attain the above object, according to a first aspect of the presentinvention, there is provided a method of producing a semiconductordevice, including the steps of forming an interconnection groove in aninsulation film formed on a substrate, stacking a copper film havingunevenness on its surface corresponding to the step difference of theinterconnection groove on the entire surface of the insulation film soas to bury the interconnection groove, interposing an electrolyticsolution including a chelating agent between a cathode member and thecopper film, applying a voltage between the cathode member functioningas a cathode and the copper film functioning as an anode to oxidize thesurface of the copper film and form a chelate film of oxidized copper,selectively removing a projecting portion of the chelate filmcorresponding to unevenness of the copper film to expose the copper filmof that projecting portion at its surface, and repeating the chelatefilm forming step and the above chelate film removing step until theprojecting portion of the copper film is flattened.

According to the above method for producing a semiconductor device, theuneven copper film surface formed when burying an interconnection grooveby copper film is oxidized by anodic oxidation. This oxidized copper ischelated by a chelating agent in an electrolytic solution. Therefore, achelate film of rather low mechanical strength able to be easily removedis formed. If removing a projecting portion of the chelate film, becausethe further exposed copper is chelated after being oxidized by anodicoxidation, flatness of the copper film is achievable by repeating thestep of removing the projecting portion of the chelate film.

Since the resistance of the chelate film is higher than copper, thecopper covered by the not removed chelate film remaining in the grooveis hard to be oxidized by anodic oxidation by passing a current, so thechelation is very slow and the chelate film is formed by anodicoxidation only at the projecting portion of the copper exposed by theremoval of the previous chelate film.

Further, because the current is supplied through an electrolyticsolution, if the potential difference between the copper film on theanode and the cathode member of the cathode is constant, the currentdensity becomes larger the shorter the distance between electrodes.Therefore, in the copper film exposed after removing the chelate film,the more projecting a part of the copper film is, the shorter theelectrode distance to the cathode member used as the cathode and thusthe higher the current density and consequently, the higher the speed ofthe anodic oxidation and the faster the chelation.

Accordingly, because of the accelerated chelation of the projectingportion of the copper film, it is able to achieve efficient flatteningand suppression of damage to the interlayer insulation film below acopper film.

The method for producing a semiconductor device according to the presentinvention preferably further includes a step, after flattening theprojecting portion of the copper film, of removing the chelate filmformed on the surface of the copper film until removing the copper filmstacked outside the interconnection groove.

Due to this, copper interconnections can be formed while suppressingdamage to the interlayer insulation film below the copper film.

In the method for producing a semiconductor device according to thepresent invention, preferably, in the step of applying a voltage byusing the cathode member as a cathode, a voltage is applied using as acathode a conductive polishing tool for removing a projecting portion ofthe chelate film.

By using a polishing tool as the cathode, efficient chelation due to theanodic oxidation and efficient removal of the chelate film can beobtained.

In the method for producing a semiconductor device according to thepresent invention, preferably, in the step of applying a voltage byusing the copper film as the anode, a voltage is applied on an anodemember contacting or close to the copper film, making the copper film ananode through the electrolytic solution.

By locally passing a current from the anode member to the copper filmthrough the electrolytic solution, a stable current can be supplied.

In this case, a current is supplied to the copper film from the anodemember via the electrolytic solution and, further, from the copper filmto the cathode member through the electrolytic solution, so the copperfilm near the cathode member is oxidized and chelated.

In the method for producing a semiconductor device according to thepresent invention, preferably, in the step of applying a voltage byusing the cathode member as a cathode, a voltage is applied using aconductive electrode plate arranged parallel with the copper film as acathode.

By arranging the electrode plate parallel with the copper film, as shownabove, in the exposed copper films, the more projecting the portion, theshorter the electrode distance. Due to the increase of the speed of theanodic oxidation caused by the increased current density, the chelationis accelerated, so efficient flattening is achievable.

In the method for producing a semiconductor device according to thepresent invention, preferably, in the step of removing the chelate film,the chelate film is removed by wiping or mechanical polishing.

Since the chelate film has a rather low mechanical strength, mechanicalpolishing involving strong pressing is not necessary. It can be easilyremoved by wiping or mechanical polishing involving only weak pressing.

In the method for producing a semiconductor device according to thepresent invention, preferably, in the step of removing the chelate film,the chelate film is removed by applying vibration to the substrate.Alternatively, in the step of removing the chelate film, the chelatefilm is removed by flushing with the electrolytic solution.

Since the chelate film has a rather low mechanical strength, it can beeasily removed not only by mechanical polishing, but also by vibrationand the flushing action of the electrolytic solution.

In the method for producing a semiconductor device according to thepresent invention, preferably, in the chelate film forming step and thechelate film removing step, a current flowing through the cathode memberand the copper film is monitored and the polishing process of the copperfilm is controlled in response to the magnitude of the current.

For example, by using a chelating agent forming a chelate film having ahigher electrical resistance than the copper film, before the projectingportion is flattened, the current between the cathode member and thecopper film increases when the projecting chelate film is removedbecause copper is exposed. When a chelate film is formed on the exposedcopper again, the value of the current decreases. This cycle isrepeated. When the copper film is flattened, because the chelate film onthe copper film is removed completely and the copper film is exposedtotally, the current reaches a maximum first, then the current valueexhibits a new maximum at each removal.

When the barrier film is exposed, since usually the resistance of thebarrier film is higher than copper, the current value begins to decreaseafter the chelate film is removed. Therefore, if stopping theapplication of voltage at the time when the current value begins todecrease, the formation of the chelate film by the anodic oxidation canbe stopped after that time, thus the progress of the polishing can becontrolled.

In addition, to achieve the above object, according to a second aspectof the present invention, there is provided a polishing method forpolishing an object having a copper film on the surface to be polished,including the steps of interposing an electrolytic solution including achelating agent between a cathode member and the polished surface,applying a voltage between the cathode member functioning as a cathodeand the polished surface functioning as an anode to oxidize the surfaceof the copper film and form a chelate film of an oxidized copper film,selectively removing a projecting portion of the chelate filmcorresponding to the shape of the copper film to expose the copper filmof that projecting portion at its surface, and repeating the abovechelate film forming step and the chelate film removing step until theprojecting portion of the copper film is flattened.

According to the polishing method of the present invention for polishingan object having a copper film on the surface to be polished, byinterposing an electrolytic solution including a chelating agent betweena cathode member and the polished surface and applying a voltage betweenthe cathode member used as a cathode and the polished surface of thepolished object used as an anode, the uneven copper surface is oxidizedby the anodic oxidation. This oxidized copper is chelated by thechelating agent in the electrolytic solution, forming a chelate film ofrather low mechanical strength thus able to be removed easily. Ifselectively removing a projecting portion of the chelate film, becausethe copper further exposed thereby is chelated after being oxidized bythe anodic oxidation, flatness of the copper film is achievable byrepeating the step of selectively removing the projecting portion of thechelate film.

Since the resistance of the chelate film is higher than copper, thecopper covered by the unmoved chelate film remaining in the groove ishard to be oxidized by the anodic oxidation by supplying a current, sothe chelation is very slow and a chelate film is formed by the anodicoxidation only at the projecting portion of copper exposed by removingthe chelate film.

Further, because the current is supplied through an electrolyticsolution, if the potential difference between the copper film on theanode and the cathode member of the cathode is constant, the currentdensity becomes larger the shorter the distance between electrodes.Therefore, in the copper film exposed after removing the chelate film,the more projecting a part of the copper film is, the shorter theelectrode distance to the cathode member used as the cathode and thusthe higher the current density and consequently, the higher the speed ofthe anodic oxidation and the faster the chelation.

Accordingly, because of the accelerated chelation of the projectingportion of-the copper film, it is possible to achieve efficientflattening and suppression of damage to an interlayer insulation filmbelow a copper film.

In addition, to achieve the above object, according to a third aspect ofthe present invention, there is provided a method for production of asemiconductor device, including the steps of forming at least a grooveor hole in an insulation film formed on a substrate, stacking a metalfilm on the insulation film so as to bury the groove or hole,interposing an electrolytic solution between a cathode member and themetal film, applying a predetermined voltage between the cathode memberused as a cathode and the metal film used as an anode, removing thesurface of the metal film, and repeating the above step of removing themetal film until the unevenness of the surface of the metal film isreduced.

Further, the method for producing a semiconductor device of the presentinvention further includes a step of forming a barrier film forpreventing diffusion of the metal film to the insulation film on theinsulation film so as to bury the groove or hole after forming thegroove or hole in the insulation film and before stacking the metal filmon the insulation film, wherein the metal film is stacked on the barrierfilm in the step of stacking the metal film on the insulation film.

Further, in the step of removing the surface of the metal film, the stepof copper film removal is repeated until the metal film stacked outsidethe groove or hole is removed.

According to the above method for producing a semiconductor device, whenprocessing the surface of a metal film buried in a groove or hole, byinterposing an electrolytic solution between a cathode member and themetal film and applying a predetermined voltage between the cathodemember used as a cathode and the metal film used as an anode, the metalfilm is oxidized by the anodic oxidation, ionized in a state of metallicions, and has a very low mechanical strength enabling it to be easilyremoved. If removing the oxidized metal film, the further exposed metalfilm is oxidized by the anodic oxidation again. By repeating the step ofremoving the metal film after the anodic oxidation, the step differenceof the metal film can be reduced.

Further, because current is supplied through an electrolytic solution,if the potential difference between the metal film of the anode and thecathode member of the cathode is constant, the current density becomeslarger the shorter the distance between electrodes. Therefore, in thecopper film exposed after removing the chelate film, the more projectingthe copper film is, the shorter the electrode distance to the cathodemember used as the cathode and thus the higher the current density.Consequently, the anodic oxidation of the projecting portion of themetal film is accelerated, the step difference of the metal film surfacecan be efficiently reduced, and the damage to the insulation film belowthe metal film can be suppressed.

In addition, to achieve the above object, according to a fourth aspectof the present invention, there is provided a polishing apparatus forpolishing an object having a copper film on the surface to be polished,comprising a polishing tool having a polishing surface and havingconductivity, a polishing tool rotating and holding means for rotatingthe polishing tool about a predetermined axis of rotation and holdingthe same, a rotating and holding means for holding a polishing objectand rotating the same about a predetermined axis of rotation, a movingand positioning means for moving and positioning the polishing tool to atarget position in a direction facing the polishing object, a relativemoving means for making the polished surface of the polishing object andthe polishing surface of the polishing tool relatively move along apredetermined plane, an electrolytic solution feeding means for feedingan electrolytic solution including a chelating agent onto the polishedsurface, and a current supplying means for supplying an electrolyticcurrent flowing through the polishing tool through the electrolyticsolution from the polished surface by using the polished surface as ananode and the polishing tool as a cathode.

According to the polishing apparatus of the present invention, forexample, if a copper film with unevenness is formed on a polishedsurface of the object to be polished, the polished surface of the copperfilm is oxidized by the anodic oxidation by the current supplying means.This oxidized copper is chelated by a chelating agent in an electrolyticsolution fed by the electrolytic solution feeding means. A chelate filmof a rather low mechanical strength and able to be easily removed isthus formed.

The moving and positioning means brings the polishing surface intocontact or proximity with the polished surface. The polishing toolrotating and holding means rotates the polishing surface and thepolished surface in a state in contact or proximity with each other.Therefore, the projecting portion of a chelate film is removed. Further,by the relative moving means, projecting portions of the chelate film onthe entire polished surface are polished and removed, therefore thepolished surface can be polished efficiently at a low polishingpressure.

In the polishing apparatus of the present invention, preferably theelectrolytic current supplying means comprises an anode member arrangedto be able to be brought into contact or proximity with the polishedsurface and supply current to the polished surface using the polishedsurface as an anode and a DC power supply supplying a predetermined DCpower between the anode member means and the polishing tool.

By locally passing a current from the anode member to the copper filmthrough the electrolytic solution, a stable current can be supplied.

In this case, a current is supplied to the copper film from the anodemember via the electrolytic solution and further from the copper film tothe cathode member through the electrolytic solution, so the copper filmnear the polishing tool serving as a cathode is oxidized and chelated.

In the polishing apparatus according to the present invention,preferably the DC power supply outputs a pulse-like voltage of apredetermined period.

For example, setting the pulse width extremely short is effective formaking the amount of the chelate film formed by the anodic oxidation perpulse very small, preventing sudden, huge anode oxidation of the copperfilm due to discharge due to a sudden change of the distance betweenelectrodes in a case of contact with unevenness of the surface or thelike, spark discharge due to a sudden change of electrical resistanceoccurring when air bubbles, particles, or the like are interposed, etc.and achieving continuity of amounts as small as possible.

In the polishing apparatus according to the present invention,preferably the anode member comprises a metal more precious than copperformed on the polished surface. Due to this, elution of the anode memberto the electrolytic solution can be prevented, and the copper film canbe actively oxidized by the anodic oxidation. Note since the cathode isessentially not eluted, it is not necessary to consider the preciousnessof the cathode.

The polishing apparatus according to the present invention preferablyfurther comprises a current detecting means for detecting a value of acurrent flowing from the polished surface to the polishing tool, morepreferably further comprises a control means for controlling a positionof the polishing tool in a direction substantially perpendicular withthe polished surface so that the value of the current becomes constanton the basis of a detection signal of the current detecting means.

By control to make the current value constant, the current densitybecomes constant constantly and thereby the amount of the chelate filmformed by the anode oxidation can be controlled constant.

In addition, to achieve the above object, according to a fifth aspect ofthe present invention, there is provided a polishing apparatus whichcomprises a polishing tool having a polishing surface in contact withthe entire surface of the polished surface of the polishing object whilerotating it and which brings the polishing object into contact with thepolished surface while rotating it so as to flatten and polish the same,the polishing apparatus comprising an electrolytic solution feedingmeans for feeding an electrolytic solution including a chelating agentonto the polishing surface and an anode electrode and a cathodeelectrode capable of supplying electric power in the polishing surfaceand flattening the polished surface by electrolytic composite polishingwhich combines electrolytic polishing by the electrolytic solution andmechanical polishing by the polishing surface.

According to the polishing apparatus of the present invention, forexample, by applying a voltage to the anode and cathode provided on thepolishing surface, a current is supplied to the copper film on thepolished surface from the anode member on the polishing surface via theelectrolytic solution and furthermore from the copper film to thecathode on the polishing surface through the electrolytic solution, sothe copper film of the polished surface near the cathode is oxidized.

This oxidized copper is chelated by the chelating agent in theelectrolytic solution fed by the electrolytic solution feeding means,whereby a chelate film of a rather low mechanical strength able to beeasily removed is formed.

By rotating the polishing surface and the polished surface respectivelyin a state contacting each other entirely or brought close to each otherentirely, projecting portions of the chelate film on the entire polishedsurface are polished and removed, therefore the polished surface can bepolished efficiently with a low polishing pressure.

In addition, to achieve the above object, according to a sixth aspect ofthe present invention, there is provided a polishing apparatus forpolishing an object having a copper film on the surface to be polished,comprising a holding means for holding the object to be polished, anelectrode plate arranged parallel with the polished surface, a vibrationapplying means for applying vibration on the polished object, anelectrolytic solution feeding means for feeding an electrolytic solutionincluding a chelating agent between the polished surface and theelectrode plate, and an electrolytic current supplying means forsupplying an electrolytic current flowing through the electrolyticsolution from the polished surface to the electrode plate by using thepolished surface as an anode and the electrode as a cathode.

According to the polishing apparatus of the present invention, forexample, if a copper film with unevenness is formed on the polishedsurface, the polished surface of the copper film is oxidized by theanodic oxidation by the current supplying means. This oxidized copper ischelated by the chelating agent in the electrolytic solution fed by theelectrolytic solution feeding means, whereby a chelate film of a ratherlow mechanical strength able to be easily removed is formed.

The projecting portions of the chelate film are selectively removed bythe vibration action on the polished object by the vibration applyingmeans. This enables efficient polishing causing little damage to thepolished object.

The polishing apparatus according to the present invention preferablyfurther comprises a current detecting means for detecting a value of acurrent flowing from the polished surface to the polishing tool. Therebythe electrolytic current can be monitored and the polishing processcontrolled, so it becomes possible to correctly grasp the state ofprogress of the polishing process.

In addition, to achieve the above object, according to a seventh aspectof the present invention, there is provided a polishing apparatus forpolishing an object having a copper film on the surface to be polished,comprising a holding means for holding the polished object, an electrodeplate arranged parallel with the polished surface, an electrolyticsolution feeding means for feeding an electrolytic solution including achelating agent between the polished surface and the electrode plate, anelectrolytic current supplying means for supplying an electrolyticcurrent flowing through the electrolytic solution from the polishedsurface to the electrode plate by using the polished surface as an anodeand the electrode as a cathode, and a flushing means for flushing theelectrolytic solution between the polished surface and the electrodeplate.

According to the polishing apparatus of the present invention, forexample, if a copper film with unevenness is formed on the polishedsurface of the object to be polished, the polished surface of the copperfilm is oxidized by the anodic oxidation by the current supplying means.This oxidized copper at an anode is chelated by the chelating agent inthe electrolytic solution fed by the electrolytic solution feedingmeans, whereby a chelate film of a rather low mechanical strength ableto be easily removed is formed.

The projecting portions of the chelate film are selectively removed by avibration action on the polished object by the vibration applying means.This enables efficient polishing causing little damage to the polishedobject.

The polishing apparatus according to the present invention preferablyfurther comprises a current detecting means for detecting a value of acurrent flowing from the polished surface to the polishing tool.Therefore, the electrolytic current can be monitored and the polishingprocess controlled, so it becomes possible to correctly grasp the stateof progress of the polishing process.

In addition, to achieve the above object, according to an eighth aspectof the present invention, there is provided a polishing apparatus forpolishing an object having a metal film on the surface to be polished,comprising a holding means for holding the polished object, a wiper forwiping the surface of the polished object, an electrolytic solutionfeeding means for feeding an electrolytic solution on the surface of thepolished object, a facing electrode arranged at a position facing thesurface of the polished object, and a current supplying means forsupplying a current between the surface of the polished object and thefacing electrode.

In addition, to achieve the above object, according to a ninth aspect ofthe present invention, there is provided a polishing apparatus forpolishing an object having a metal film on the surface to be polished,comprising a holding means for holding the polished object, a wiper forwiping the surface of the polished object, a relative moving means forrelatively moving the surface of the polishing object and the wiper, anelectrolytic solution feeding means for feeding an electrolytic solutionon the surface of the polished object, a facing electrode arranged at aposition facing the surface of the polished object, and a currentsupplying means for supplying a current between the surface of thepolished object and the facing electrode.

The relative moving means presses the wiper on the surface of thepolished object and rotates the wiper relative to a predetermined centeraxis of rotation.

Alternatively, the relative moving means presses the wiper against thesurface of the polished object and horizontally moves the wiper in thesurface of the polished object.

Alternatively, the relative moving means rotates the holding meansrelative to a predetermined center axis of rotation.

Alternatively, the relative moving means horizontally moves the holdingmeans in a surface parallel with the surface of the wiper.

According to the above polishing apparatuses according to the presentinvention, for example, when a metal film is formed on the polishedsurface of the polishing object, an electrolytic solution is fed ontothe surface of the polishing object by the electrolytic solution feedingmeans, and a current is supplied between the surface of the polishingobject and the facing electrode by the current supplying means, so themetal film is oxidized by the anodic oxidation, ionized into-a state ofmetallic ions, and has a very low mechanical strength enabling it to beeasily removed.

Further, by wiping the surface of the oxidized metal film using a wiper,the oxidized metal is removed, therefore, the polishing object can bepolished efficiently even at a low pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object and features of the present invention will be moreapparent from the following description of the preferred embodimentsgiven with reference to the accompanying drawings, wherein:

FIGS. 1A to 1C are sectional views of the steps of the method ofproduction of a semiconductor device of the present invention, whereFIG. 1A shows the step for forming an insulation film on a semiconductorsubstrate, FIG. 1B shows the step for forming contact holes andinterconnection grooves, and FIG. 1C shows the step for forming abarrier film;

FIGS. 2D and 2E are views of the steps continuing from FIGS. 1A to 1C,where FIG. 2D shows the step of forming a copper film as a seed film,while FIG. 2E shows the step of forming a copper film;

FIGS. 3F and 3G are views of the steps continuing from FIGS. 2D and 2E,where FIG. 3F shows the step of anodic oxidation of the copper film,while FIG. 3G shows the step of forming a chelate film;

FIGS. 4H and 4I are views of the steps continuing from FIGS. 3F and 3G,where FIG. 4H shows the step of removing projecting portions of thechelate film, while FIG. 4I shows the step of re-forming a chelate film;

FIGS. 5J to 5L are views of the steps continued from FIGS. 4H and 4I,where FIG. 5J shows the step of flattening the copper film, FIG. 5Kshows the step of removing excess copper film, and FIG. 5L shows thestep of exposing the barrier film;

FIG. 6 is a view of the configuration of a polishing apparatus accordingto a first embodiment of the present invention;

FIG. 7 is an enlarged view of the internal configuration of a polishingtool holding means of a polishing apparatus according to the firstembodiment of the present invention;

FIG. 8A is a bottom view of an electrode plate used in a polishingapparatus according to the first embodiment of the present invention,while FIG. 8B is an enlarged view of the vicinity of the electrodeplate;

FIG. 9 is a view of the relationship between a polishing tool and awafer;

FIG. 10 is a schematic view for explaining the electrolytic polishing ofa polishing apparatus according to the first embodiment of the presentinvention;

FIG. 11 is an enlarged sectional view of the circular portion C of FIG.10;

FIG. 12 is an enlarged sectional view of the circular portion D of FIG.11;

FIG. 13 is a view of a first modification of the polishing apparatusaccording to the present invention;

FIG. 14 is a view of a second modification of the polishing apparatusaccording to the present invention;

FIG. 15 is a view of a third modification of a conventional CMPapparatus of a polishing apparatus according to the present invention;

FIG. 16 is a view for explaining an electrolytic composite polishingoperation by the polishing apparatus shown in FIG. 15;

FIG. 17 is a view of another example of an electrode configuration of apolishing pad;

FIG. 18 is a view of still another example of an electrode configurationof a polishing pad;

FIG. 19 is a schematic view of the configuration of a polishingapparatus according to a second embodiment of the present invention;

FIG. 20 is a schematic view of the configuration of a polishingapparatus according to a third embodiment of the present invention;

FIG. 21 is a view of a configuration of a polishing apparatus accordingto a fourth embodiment of the present invention;

FIG. 22A and FIG. 22B shows measurement results in a fifth embodiment;

FIG. 23 shows measurement results in a sixth embodiment;

FIG. 24 shows measurement results in a seventh embodiment;

FIGS. 25A to 25C are sectional views of steps of the method of formationof copper interconnections by a dual damascene process according to anexample of the related art, where FIG. 25A shows the step of forming aninsulation film, FIG. 25B shows the step of forming contact holes andinterconnection grooves, and FIG. 25C shows the step of forming abarrier film;

FIGS. 26D to 26F are views of the steps continuing from FIGS. 25A to25C, where FIG. 26D shows the step of forming a seed film, FIG. 26Eshows the step of forming an interconnection layer, and FIG. 26F showsthe step of forming interconnections;

FIG. 27 is a sectional view for explaining dishing occurring inpolishing of a copper film by CMP;

FIG. 28 is a sectional view for explaining erosion occurring inpolishing of a copper film by CMP;

FIG. 29 is a sectional view for explaining a recess occurring inpolishing of a copper film by CMP; and

FIG. 30 is a sectional view for explaining a scratch SC and chemicaldamage CD occurring in polishing of a metal film by CMP.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, a description will be made of preferred embodiments of a methodfor producing and a method of polishing a semiconductor device and apolishing apparatus of the present invention by referring to thedrawings.

First Embodiment

A description will be made of embodiments of the present invention bytaking as an example the case where the present invention is applied toa process of formation of metal interconnections by a dual damasceneprocess in a method of production of a semiconductor device.

Polishing Method

First, as shown in FIG. 1A, for example an interlayer insulation film102 made of for example a silicon oxide film (SiO₂) is formed by a lowpressure chemical vapor deposition (LP-CVD) process by using for exampletetraethyl orthosilicate (TEOS) as the reaction source on a silicon orother semiconductor substrate 101 on which a not illustrated impuritydiffusion region or an interconnection is suitably formed.

Note that as the interlayer insulation film 102, use can be made of aso-called low-k (low dielectric constant) material, in addition to aTEOS (tetraethyl orthosilicate) film and a silicon nitride film formedby a CVD process.

Here, the low dielectric constant materials include SiF, SiOCH,polyarylether, porous silica, or polyimide.

Next, as shown in FIG. 1B, contact holes CH communicating with theimpurity diffusion region of the semiconductor substrate 101 andinterconnection grooves M are formed by using well-knownphotolithography and etching. Note that the depth of the interconnectionuse grooves M is for example about 800 nm.

Next, as shown in FIG. 1C, a barrier film 103 is formed on the surfaceof the interlayer insulation film 102 and in the contact holes CH andthe interconnection grooves M. This barrier film 103 is formed by amaterial such as Ta, Ti, W, Co, Si, Ni, an alloy of compounds of thesemetals with nitrogen or phosphor such as TaN, TiN, WN, CoW, CoWP, TiSiN,NiWP, or others, or a stack of films comprised of these materials. Abarrier film comprised of these material is fabricated to a thickness offor example about 25 nm by physical vapor deposition (PVD) or CVD usinga well-known sputtering system, a vacuum vapor deposition system, or thelike.

The barrier film 103 is provided in order to prevent the diffusion ofthe material comprising the interconnections into the interlayerinsulation film 102 and to increase the adhesion with the interlayerinsulation film 102. Particularly, as in the present embodiment, whenthe interconnection material is copper and the interlayer insulationfilm 102 is silicon oxide, since copper has a large diffusioncoefficient as compared in a silicon oxide film, it can be easilyoxidized. This should be prevented.

Next, as shown in FIG. 2D, a seed film 104 made of a material the sameas the material for forming the copper interconnections is formed on thebarrier film 103 to a thickness of for example about 150 nm bywell-known sputtering. The seed film 104 is formed for laterelectroplating. For example, it is formed so as to accelerate the growthof metal grains when burying the interconnection grooves and the contactholes with a metal.

Next, as shown in FIG. 2E, an interconnection layer 105 made of Al, W,WN, Cu, Au, or Ag, or an alloy film of these metals, is formed on thebarrier film 103 to a thickness of for example about 1600 nm so as tobury the contact holes CH and the interconnection grooves M. Theinterconnection layer 105 is preferably formed by electroplating orelectroless plating, but it is also possible to form the interconnectionlayer 105 by CVD, PVD, sputtering, or the like. Note that the seed film104 is integrally formed with the interconnection layer 105.

Due to the burying of the contact holes CH and the interconnectiongrooves M, unevenness having a height of for example about 800 nm iscaused on the surface of the interconnection layer 105.

Below, an explanation is made for example of a case where copper isstacked as the interconnection layer.

The above process is carried out in a way similar to the related art,but in the polishing method of the present invention, the excess metalfilm 103 present on the interlayer insulation film 102 is removed by notchemical mechanical polishing, but electrolytic composite polishingusing an electrolytic action. Specifically, the copper film is oxidizedby the anodic oxidation, and a chelate film is formed on the surfacethereof.

The method for forming the chelate film, as shown in FIG. 3F, includesthe steps of arranging a cathode member 120 parallel with the copperfilm 105 and interposing an electrolytic solution EL including achelating agent for chelating copper as an electrolyte or an additivebetween the cathode member 120 and the copper film 105. Note thatstarting from FIG. 4, the cathode member 120 and the electrolyticsolution EL are not shown in the figures.

Further, a brightener, copper ions, etc. can be added to an electrolyticsolution in addition to the above additives.

The temperature of the electrolytic solution EL is controlled, and thedegree of oxidation of the surface of the metal film, chelating filmformation, and wiping are optimized.

Here, as the chelating agent, use may be made of for example quinaldineacid of chemical formula (1), glycin of chemical formula (2), citricacid of chemical formula (3), oxalic acid of chemical formula (4),propionic acid of chemical formula (5), and so on.

NH₂CH₂COOH  (2)

(COOH)₂  (4)C₂H₅COOH  (5)

The copper film 105 serving as the anode forms CuO by anodic oxidation.Here, the distance d1 between a projecting portion on the surface of thecopper film 105 and the cathode member 120 is shorter than the distanced2 between a recessed portion on the surface of the copper film 105 andthe cathode member 120, so when the potential difference between thecathode member 120 and the copper film 105 is constant, the currentdensity at the projecting portion is greater than that at the recessedportion, therefore, the anodic oxidation is accelerated.

As shown in FIG. 3G, the surface of the oxidized copper film (CuO) 105is chelated by the chelating agent in the electrolytic solution. Whenquinaldine acid is used as the chelating agent, a film made from achelated compound of the chemical formula (6) is formed. When glycin isused, a film made from a chelate compound of the chemical formula (7) isformed. Any of these chelate films 106 has an electric resistance higherthan copper and a very low mechanical strength. Accordingly, after achelate film 106 is formed on the copper film 105, the value of thecurrent from the copper film 105 to the cathode member 120 via theelectrolytic solution EL decreases. Before the anodic oxidation, copperchelation is suppressed.

Next, as shown in FIG. 4H, when the projecting portions of the chelatefilm 106 formed on the surface of the copper film 105 are removed bywiping, mechanical polishing, etc., the electrolytic solution EL mayalso include a not shown slurry. Further, because the mechanicalstrength of the chelate film 106 is very low, it can be easily removedeven by applying vibration to the substrate 101 or by jetting theelectrolytic solution.

Because the projecting portion of the copper film 105 of the lowelectric resistance is exposed in the electrolytic solution at thattime, the value of the current flowing from the copper film 105 to thecathode member 120 via the electrolytic solution EL rises.

Next, as shown in FIG. 4I, because of the low electric resistance andshort distance to the cathode 120, the projecting portion of the copperfilm 105 exposed in the electrolytic solution is intensively oxidized bythe anodic oxidation and the oxidized copper is chelated. Then, thecurrent flowing from the copper film 105 to the cathode member 120 viathe electrolytic solution EL decreases again.

After that, the projecting portions of the chelate film 106 areselectively removed by the previously mentioned wiping, mechanicalpolishing, etc., the exposed copper film 105 is intensively oxidized andchelated, and the projecting portions of the chelate film 106 areselectively removed. These steps are repeated. In this process, thecurrent from the copper film 105 flowing to the cathode member 120 viathe electrolytic solution EL rises and falls together with removal andformation of the chelate film 106, respectively.

Next, as shown in FIG. 5J, after the above step, the copper film 105 isflattened. The flattened copper film 105 is removed from the entiresurface by wiping, mechanical polishing, etc., whereby the currentflowing from the copper film 105 to the cathode member 120 via theelectrolytic solution EL reaches its maximum once during this process.

Next, as shown in FIG. 5K, the chelate film formed by anodic oxidationon the entire surface of the flattened copper film 105 continues to beremoved until the excess copper film 105 on the barrier film 103disappears completely.

Next as shown in FIG. 5L, the entire copper film 105 is removed by forexample the aforethe wiping, mechanical polishing, etc. to expose thesurface of the barrier film 103. At this time, as the barrier film 103has a higher electric resistance than the copper film. 105, the currentstarts to decline after the removal of the chelate film 106. At the timeof starting to decline (near the end), the applied current is reducedfirst, then the application of current is stopped to stop the chelationdue to the anodic oxidation. The processes up to here complete theflattening of the initial unevenness of the surface of the copper film105.

Next, the barrier film 103 stacked outside the interconnection groovesis removed, whereby the copper interconnections are formed.

According to the polishing method according to the present embodiment,since the polishing rate of the polishing is assisted electrochemicallyassisted, the polishing is possible at a low polishing pressure comparedwith conventional chemical mechanical polishing. Even in comparison withsimple mechanical polishing, this is highly advantageous in reducingscratches, reducing step differences, reducing dishing and erosion, etc.

Further, since the polishing is possible at a low pressure, it isextremely useful in a case where an organic film of a low dielectricconstant or a porous insulation film of a low dielectric constant, whichhave low mechanical strengths and are easily broken by conventionalchemical mechanical polishing, is used for the interlayer insulationfilm 102.

In the chemical mechanical polishing of the related art, when using aslurry containing alumina particles etc., the alumina particles mayremain without wear after contributing to the CMP processor they may beburied in the surface of the copper (particle). In the polishing methodof the present invention, however, since the chelate film formed on thesurface has a very low mechanical strength it can be removed effectivelyeven by mechanical polishing or wiping using a chelating agent notcontaining a polishing abrasive as the electrolytic solution.

Further, by monitoring the electrolytic current, the polishing processcan be controlled, so it becomes possible to correctly grasp the stateof progress of the polishing process.

The polishing method according to the present invention is not limitedto the above embodiment. As described above, it can also be applied tointerconnections comprised of, for example, Al, W, WN, Cu, Au, or Ag, oran alloy film of these metals, in addition to copper. It can also beapplied to polishing of a barrier film comprised of the above materials.

Further, the polishing method according to the present invention canalso be applied to polishing of numerous metal films used for other thaninterconnections.

Further, various modifications can be made to the type of the chelatingagent, the type of the cathode member, and so on without departing fromthe basic concept of the present invention.

Further, numerous modifications can be made without departing from thebasic concept and scope of the invention, such as the type of thechelating agent, the type of the cathode member, and so on.

Further, the method for producing a semiconductor device is not limitedto the above embodiment either. For example, the method of polishing ametal film is not limited in any way. In the present embodiment, a dualdamascene process was explained as an example, but the present inventionis also applicable to a single damascene process. In addition, numerousmodifications can also be made without departing from the basic conceptand scope of the invention in, such as, methods for fabricating contactholes or interconnection grooves and methods for fabricating a copperfilm and a barrier film.

Configuration of Polishing Apparatus

FIG. 6 is a view of the configuration of a polishing apparatus accordingto an embodiment of the present invention.

The polishing apparatus shown in FIG. 6 is provided with a polishinghead H, an electrolytic power supply 61, a controller 55 having afunction of controlling the entire polishing apparatus, a slurry feeder71, and an electrolytic solution feeder 81.

Note that, although not illustrated, the polishing apparatus isinstalled in a clean room, and a loading/unloading port for loading andunloading a wafer cassette storing wafers serving as the polishingobjects in or out of the clean room is provided in the clean room.Further, a wafer conveyance robot for transferring the wafer between thewafer cassette loaded in the clean room through this loading/unloadingport and the polishing apparatus is arranged between theloading/unloading port and the polishing apparatus.

The polishing head H is provided with a polishing tool holder 10 (apolishing tool rotating and holding means) for holding and rotating thepolishing tool 11, a Z-axis positioning mechanism 30 (a moving andpositioning means) for positioning the polishing tool holder 10 to atarget position in the Z-axial direction, and an X-axis movementmechanism 40 (a rotating and holding means and a relative moving means)for holding and rotating a wafer as the polishing object and moving itin the X-axial direction.

The Z-axis positioning mechanism 30 has a Z-axis servo motor 31 fixed toa not illustrated column, a ball screw shaft 31 a connected to theZ-axis servo motor 31, a Z-axis slider 32 which is connected to a holder33 and a main shaft motor 14 and formed with a screw portion screwedinto the ball screw shaft 31 a, and a guide rail 33 arranged in a notillustrated column for holding the Z-axis slider 32 so that it canfreely move in the Z-axial direction.

The Z-axis servomotor 31 is supplied with a drive current from a Z-axisdriver 51 connected to the Z-axis servomotor 31 to be driven to rotate.The ball screw shaft 31 a is provided along the Z-axial direction, withone end of it connected to the Z-axis servo motor 31 and with the otherend rotatably held by the holding member provided in the not illustratedcolumn, and is screwed into the screw portion of the Z-axis slider 32between the ends.

Due to the above configuration, by being driven by the Z-axis servomotor 31, the ball screw shaft 31 a is rotated. The polishing tool 11held at the polishing tool holder 10 is moved and positioned via theZ-axis slider 32 to any position in the Z-axial direction. Thepositioning precision of the Z-axis positioning mechanism 30 is set at aresolution of about 0.1 μm.

The X-axis movement mechanism 40 has a wafer table 42 for chucking thewafer W, a holder 45 for rotatably holding the wafer table 42, a drivemotor 44 for supplying a drive force for rotating the wafer table 42, abelt 46 for connecting the drive motor 44 and a rotation shaft of theholder 45, a polishing pan 47 provided in the holder 45, an X-axisslider 48 at which the drive motor 44 and the holder 45 are disposed, anX-axis servo motor 49 mounted on a not illustrated base, a ball screwshaft 49 a connected to the X-axis servo motor 49, and a moveable member49 b connected to the X-axis slider 48 and with a screw portion screwedinto the ball screw shaft 49 a formed therein.

The wafer table 42 holds the wafer W by for example a vacuum suctionmeans.

The polishing pan 47 is provided for collecting the used electrolyticsolution and slurry or other liquid.

The drive motor 44 is connected to the table driver 53 and is driven bysupply of the drive current from the table driver 53. By controllingthis drive current, the semiconductor substrate table 42 can be rotatedat a predetermined rotation speed.

The X-axis servomotor 49 is driven to rotate by the drive currentsupplied from an X-axis driver 54 connected to the X-axis servomotor 49.The X-axis slider 48 moves in the X-axial direction via the ball screwshaft 49 a and the moveable member 49 b. At this time, by controllingthe drive current supplied to the X-axis servo motor 49, the control ofthe speed of the wafer table 42 in the X-axial direction becomespossible.

The slurry feeder 71 feeds the slurry to the wafer W through a notillustrated feed nozzle. As the slurry, for polishing a copper film, forexample use is made of one comprised of an aqueous solution havingoxidizing power based on hydrogen peroxide, iron nitrate, potassiumiodate, etc. to which aluminum oxide (alumina), cerium oxide, silica,germanium oxide, or the like is added as the polishing abrasive. Notethat the slurry may be supplied only when necessary.

The electrolytic solution feeder 81 feeds an electrolytic solution ELincluding a chelating agent to the wafer W through a not illustratedfeed nozzle.

The electrolyte can be one based on an organic solvent or an aqueoussolution.

The acid used for the electrolyte may include for example coppersulfate, ammonium sulfate, phosphoric acid, and so on. Examples ofalkali include ethyldiamine, NaOH, KOH, and so on.

Further, as the electrolyte, use can also be made of a dilute mixture oforganic solvents including ethanol, methanol, glycerin, ethylene glycol,and so on.

The additives include Cu ion series substance, a brightener, or achelating agent.

For the brightener, use can be made of sulphuric series, copper ionseries such as copper hydroxide and copper phosphate, chlorine ionseries such as hydrochloric acid and so on, benzotriazole (BTA), orpolyethylene glycol.

As the chelating agent, for example, quinoline, anthranilic acid, etc.,can be used in addition to the aforethe quinaldine acid, glycin, citricacid, oxalic acid, propionic acid, and so on.

FIG. 7 is a view of the internal structure of the polishing tool holder10 of the polishing tool according to the present embodiment.

The polishing tool holder 10 is provided with the polishing tool 11, aflange member 12 for holding the polishing tool 11, the holder 13 forholding the flange member 12 so that it can freely rotate with respectto a main shaft 13 a, a main shaft motor 14 for rotating the main shaft13 a held at the holder 13, and a cylinder device 15 provided on themain shaft motor 14.

The main shaft motor 14 is made of for example a direct drive motor. Anot illustrated rotor of this direct drive motor is connected to themain shaft 13 a.

Further, the main shaft motor 14 has a through hole at its center intowhich a piston rod 15 b of the cylinder device 15 is inserted. The mainshaft motor 14 is driven by the drive current supplied from a main shaftdriver 52.

The holder 13 is provided with for example an air bearing. The mainshaft 13 a is rotatably held by this air bearing. Also, the main shaft13 a of the holder 13 has a through hole at its center into which thepiston rod 15 b is inserted.

The cylinder device 15 is fixed on the case of the main shaft motor 14and houses a piston 15 a. The piston 15 a is driven in either directionof the arrows A1 and A2 by for example air pressure fed into thecylinder device 15.

The piston rod 15 b is connected to this piston 15 a. The piston rod 15b passes through the center of the main shaft motor 14 and the holder 13and projects from the opening 12 a of the flange member 12.

The front end of the piston rod 15 b has a pressing member 21 connectedto this. This pressing member 21 is connected to the piston rod 15 b bya connecting mechanism that can change in posture within a predeterminedrange.

The pressing member 21 can abut against a circumferential edge of anopening 22 a of an insulation plate 22 arranged at a facing position andpresses against the insulation plate 22 by the drive of the piston rod15 b to the direction indicated by the arrow A2.

At the center portion of the piston rod 15 b of the cylinder device 15is formed a through hole. A conductive shaft 20 is inserted into thethrough hole and fixed with respect to the piston rod 15 b.

The conductive shaft 20 is formed by a conductive material. An upper endside passes through the piston 15 a of the cylinder device 15 andextends to a rotary joint 16 provided on the cylinder device 15, while alower end side passes through the piston rod 15 b and the pressingmember 21 and extends to the electrode plate 23 and is connected to theelectrode plate 23.

The conductive shaft 20 is formed at its center with a through hole.This through hole forms a feed nozzle for feeding a chemical polishingagent (slurry) and the electrolytic solution containing a chelatingagent onto the wafer W.

Further, the conductive shaft 20 performs the role of electricallyconnecting the rotary joint 16 and the electrode plate 23.

The rotary joint 16 is electrically connected to a plus pole of theelectrolytic power supply 61 and maintains the power supply to theconductive shaft 20 even when the conductive shaft 20 rotates.

The electrode plate 23 is held at its upper surface side at theinsulation plate 22, an outer circumference of the electrode plate 23 isfitted to the insulation plate 22, and the scrub member 24 is adhered tothe lower surface side.

The insulation plate 22 is formed by an insulation material such as aceramic. This insulation plate 22 is connected to the main shaft 13 a bya plurality of rod-like connecting members 26. The connecting members 26are arranged at equal intervals from the center axis of the insulationplate 22 at predetermined radial positions and held moveably withrespect to the main shaft 13 a of the holder 13. For this reason, theinsulation plate 22 can move in the axial direction of the main shaft 13a.

Further, the insulation plate 22 and the main shaft 13 a are connectedby a elastic member 25 made of for example a coil spring correspondingto each connecting member 26.

By employing a configuration in which the insulation plate 22 is mademoveable with respect to the main shaft 13 a of the holder 13 and inwhich the insulation plate 22 and the main shaft 13 a are connected bythe elastic member 25, when feeding high pressure air to the cylinderdevice 15 and moving the piston rod 15 b downward in the directionindicated by the arrow A2, the pressing member 21 pushes the insulationplate 22 downward against a recovery force of the elastic member 25, andthe scrub member 25 moves downward together with this.

When stopping the feed of the high pressure air to the cylinder device15, the insulation plate 22 rises due to the recovery force of theelastic member 25 and the scrub member 24 rises together with this.

The polishing tool 11 is tightly fixed to an annular lower end surface12 b of the flange member 12. This polishing tool 11 is formed in theshape of a wheel and provided with an annular polishing surface 11 a atits lower end surface. The polishing tool 11 has conductivity and ispreferably formed by a relatively soft material. For example, it can beformed by a porous body made of carbon with a binder matrix (bindingagent) itself which has conductivity or a resin such as a melamineresin, epoxy resin, or polyvinyl acetal (PVA) containing a conductivematerial such as sintered copper or a metal compound.

The polishing tool 11 is directly connected to the flange member 12having conductivity and supplied with power from the conductive brush 27contacting the flange member 12.

Namely, the conductive member 28 provided at the main shaft motor 14 andthe side surface of the holder 13 is electrically connected to the minuspole of the electrolytic power supply 61, while the conductive brush 27provided in the conductive member 28 is in contact with the upper endsurface 12 c of the flange member 12. Due to this, the polishing tool 11is electrically connected to the electrolytic power supply 61 via theconductive member 28, conductive brush 27, and the flange member 12.

The electrolytic power supply 61 (current supplying means) is a devicefor applying a predetermined voltage between the rotary joint 16 and theconductive member 28 described above. By the application of voltagebetween the rotary joint 16 and the conductive member 28, a potentialdifference occurs between the polishing tool 11 and the scrub member 24.

The electrolytic power supply 61 is not a constant voltage power supplyfor continuously outputting a constant voltage. It is preferable to usea power supply outputting a voltage pulse at a constant period, forexample, a DC power supply including a switching regulator circuit.

Concretely, use is made of a power supply for outputting the pulse-likevoltage at the constant cycle and capable of suitably changing the pulsewidth. As an example, use is made of one having an output voltage of DC150V and a maximum output current of 2 to 3A and capable of changing thepulse width to either of 1, 2, 5, 10, 20, or 50 μs.

The pulse-like voltage output having a short width as described above isset in order to make the amount of anodic oxidation per pulse verysmall. Namely, it is effective for achieving a continuity of smallamounts of anodic oxidation for preventing or suppressing as much aspossible a sudden huge amount of anodic oxidation of the copper filmdue, for example, to a discharge due to a sudden change of aninter-electrode distance seen in the unevenness of the copper filmformed on the surface of the wafer W or in a case of contact or the likeand a spark discharge due to a sudden change of an electrical resistanceoccurring when air bubbles, particles, or the like are interposed.

Further, the output voltage is relatively high in comparison with theoutput current, therefore a certain safety margin can be obtained insetting the inter-electrode distance. Namely, even if theinter-electrode distance slightly changes, since the output voltage ishigh, the change in the current is small.

Note that the applied pulse-like voltage is not limited to the aboveexample. A periodical pulse-like voltage having a rectangular,sinusoidal, sawtooth, or PAM waveform may be applied.

The electrolytic power supply 61 is provided with an ammeter 62 as acurrent detecting means of the present invention. This ammeter 62 isprovided so as to monitor the electrolytic current flowing through theelectrolytic power supply 61 and outputs a monitored current valuesignal 62 s to the controller 55.

Further, the electrolytic power supply 61 may also be provided with aresistance meter as a resistance value detecting means replacing thecurrent detecting means. Its function is the same as that of the currentdetecting means.

The controller 55 has the function of controlling the entire polishingapparatus. Specifically, it outputs a control signal 52 s to the mainshaft driver 52 to control the rotation speed of the polishing tool 11,outputs a control signal 51 s to the Z-axis driver 51 to control thepositioning of the polishing tool 11 in the Z-axial direction, outputs acontrol signal 53 s to the table driver 53 to control the rotation speedof the wafer W, and outputs a control signal 54 s to the X-axis driver54 to control the speed of the wafer W in the X-axial direction.

Further, the controller 55 controls the operation of the electrolyticsolution feeder 81 and the slurry feeder 71 to control the feedingoperation of the electrolytic solution EL and the slurry SL to thepolishing head.

Further, the controller 55 is able to control the output voltage of theelectrolytic power supply 61, the frequency of the output pulse, thewidth of the output pulse, etc.

Further, the controller 55 receives as input a current value signal 62 sfrom the ammeter 62 of the electrolytic power supply 61. Based on thecurrent value signal 62 s, the controller 55 grasps the state ofprogress of the polishing of the copper film and controls the operationof the polishing apparatus. Specifically, it controls the Z-axis servomotor 31 to position the polishing tool 11 in a direction perpendicularto the polished surface by using the current value signal 62 s as afeedback signal so that the electrolytic current obtained from thecurrent value signal 62 s becomes constant or controls the operation ofthe polishing apparatus so as to stop the polishing based on the currentvalue specified by the current value signal 62 s.

A periodical pulse-like voltage can be applied so that the currentflowing through the cathode member and the metal film changes in astep-like manner. For example, at the beginning of the process ofremoving the metal film, a periodical pulse-like voltage is applied sothat the current flowing through the cathode member and the metal filmrises gradually. Due to this, application of an instantaneous highvoltage at the time of starting the application and the decline therebyof the surface condition of the metal film after removal can beprevented.

Further, near the end of the process of removing a metal film, thecurrent value signal 62 s becomes small. When the current value signal62 s becomes even smaller than a predetermined threshold, control isperformed to reduce the output pulsed voltage near the end. After that,a control signal is output to the electrolytic power to stop the pulseoutput.

A control panel 56 connected to the controller 55 is used for inputtinga variety of data by an operator or displaying the monitored currentvalue signal 62 s.

Here, FIG. 8A is a bottom view of an example of the structure of theelectrode plate 23, and FIG. 8B is a sectional view of the positionalrelationships among the electrode plate 23, conductive shaft 20, scrubmember 24 (cleaning member), and insulation member (plate) 22.

As shown in FIG. 8A, a circular opening 23 a (feed nozzle) is formed atthe center portion of the electrode plate 23. A plurality of grooves 23b are formed radially extending in a radial direction of the electrodeplate 23 around this opening 23 a.

Further, as shown in FIG. 8B, the opening 23 a of the electrode plate 23has the lower end of the conductive shaft 20 fitted and fixed to it.

By employing such a configuration, the slurry and the electrolyticsolution fed through a feed nozzle 20 a formed at the center of theconductive shaft 20 are diffused through the grooves 23 b over theentire surface of the scrub member 24.

Namely, when the slurry and the electrolytic solution are fed to theupper surface of the scrub member 24 through the feed nozzle 20 a formedat the center of the conductive shaft 20 during rotation of theelectrode plate 23, conductive shaft 20, scrub member 24, and theinsulation member (plate) 22, the slurry and the electrolytic solutionspread to the entire upper surface of the scrub member 24.

Note that the scrub member 24 and the feed nozzle 20 a of the conductiveshaft 20 correspond to a concrete example of the electrolytic solutionfeeding means of the present invention. Further, the electrode plate 23,conductive shaft 20, and the rotary joint 15 correspond to a concreteexample of the power supplying means of the present invention.

The scrub member 24 adhered to the bottom surface of the electrode plate23 is formed by a material capable of absorbing the electrolyticsolution and the slurry and passing them from the upper surface to thelower surface. Further, this scrub member 24 has a surface forcontacting and scrubbing the wafer W. It is formed by for example a softbrush-like material, sponge-like material, or a porous material so asnot to cause a scratch etc. in the surface of the wafer W. For example,there can be mentioned a porous body made of a resin such as a urethaneresin, a melamine resin, an epoxy resin, or polyvinyl acetal (PVA).

FIG. 9 is a view of the positional relation of the polishing tool 11 andthe wafer in the course of polishing.

The center axis of the polishing tool 11, for example, is inclined withrespect to the wafer W with a minute angle. Further, the main shaft 12 aof the holder 13 is inclined with respect to the main surface of thewafer W in the same way as the inclination of the polishing surface 11a. For example, by adjusting an attachment posture of the holder 13 tothe Z-axis slider 32, a minute inclination of the main shaft 12 a can becreated.

In this way, by making the center axis of the polishing tool 11 inclinewith respect to the main surface of the wafer W with a minute angle,when pushing the polishing surface 11 a of the polishing tool 11 againstthe wafer W with a predetermined polishing pressure F, the effectivecontact area is maintained constant.

The polishing apparatus according to the present embodiment makes partof the polishing surface 11 a of the polishing tool 11 partially actupon the surface of the wafer W, uniformly scans the effective contactarea on the surface of the wafer W, and uniformly polishes the entiresurface of the wafer W.

Next, an explanation will be made of the polishing operation (polishingmethod) by the polishing apparatus by taking as an example a case wherethe copper film formed on the surface of the wafer W is polished. FIG.10 is a schematic view of a state where the polishing tool 11 is moveddownward in the z-axial direction in the polishing apparatus 1 to bebrought into contact with the surface of the wafer W.

First, the wafer W is chucked on the wafer table 42, and the wafer table42 is driven to rotate the wafer W at a predetermined speed.

Further, the wafer table 42 is moved in the X-axial direction, thepolishing tool 11 attached to the flange portion 12 is positioned at apredetermined position above the wafer W, and the polishing tool 11 isrotated at the predetermined rotation speed. When the polishing tool 11is rotated, the insulation plate 22, electrode plate 23, and scrubmember 24 connected to the flange portion 12 are driven to rotate.Further, the pressing member 21 pressing against the scrub member 24,piston rod 15 b, piston 15 a, and the conductive shaft 20 simultaneouslyrotate.

From this state, when the slurry SL and the electrolytic solution EL arefed to the feed nozzle 20 a in the conductive shaft 20 from the slurryfeeder 71 and the electrolytic solution feeder 81, the slurry SL and theelectrolytic solution EL are fed from the entire surface of the scrubmember 24.

The polishing tool 11 is moved downward in the Z-axial direction and thepolishing surface 11 a of the polishing tool 11 is brought into contactto the surface of the wafer W and pressed by a predetermined polishingpressure.

Further, the electrolytic power supply 61 is activated, a minuspotential is applied to the polishing tool 3 through the conductivebrush 27, and a plus potential is applied to the scrub member 24 throughthe rotary joint 16.

Further, high pressure air is fed to the cylinder device 15 to move thepiston rod 15 b downward in the direction indicated by the arrow A2 ofFIG. 7, and the bottom surface of the scrub member 24 is moved up to theposition to be brought into contact or proximity with the wafer W.

The wafer table 42 is moved in the X-axial direction with apredetermined speed pattern from this state, whereby the entire surfaceof the wafer W is uniformly polished.

FIG. 11 is an enlarged view of the area in a circle C of FIG. 10, andFIG. 12 is an enlarged view of the area in a circle D of FIG. 11.

As shown in FIG. 11, the scrub member 24, used as the anode, carriescurrent to the copper film MT formed on the wafer W via the electrolyticsolution EL or by direct contact. Further, the polishing tool 11, usedas the cathode, carries current to the copper film MT formed on thewafer W via the electrolytic solution EL or by direct contact. Notethat, as shown in FIG. 11, there is a gap δ_(b) between the copper filmMT and the scrub member 24. Further, as shown in FIG. 12, there is a gapδ_(w) between the copper film MT and the polishing surface 11 a of thepolishing tool 11.

As shown in FIG. 11, the insulation plate 22 is interposed between thepolishing tool 11 and the scrub member 24 (electrode plate 23), but theresistance RO of the insulation plate 22 is very large, accordingly, thecurrent i₀ flowing from the scrub member 24 via the insulation plate 22to the polishing tool 11 is substantially zero, namely no current flowsto the polishing tool 11 from the scrub member 24 via the insulationplate 22.

For this reason, the current flowing from the scrub member 24 to thepolishing tool 11 is branched into a current i₁ which directly flowsthrough a resistance R1 in the electrolytic solution EL to the polishingtool 11 and a current i₂ which flows from an interior of theelectrolytic solution EL through the copper film formed on the surfaceof the wafer W to the electrolytic solution EL again and to thepolishing tool 11.

When the current i₂ flows in the surface of the copper film MT, thecopper comprising the copper film MT is oxidized by anodic oxidation bythe electrolytic action of the electrolytic solution EL and is chelatedby a chelating agent in the electrolytic solution EL.

Here, the resistance R1 in the electrolytic solution EL becomesextremely large in proportion to a distance d between the scrub member24 as the anode and the polishing tool 11 as the cathode. For thisreason, by making the inter-electrode distance d sufficiently largerthan the gap δ_(b) and the gap δ_(w), the current i₁ which directlyflows through the resistance R1 in the electrolytic solution EL to thepolishing tool 11 becomes very small, the current i₂ becomes large, andalmost all of the electrolytic current passes through the surface of thecopper film MT. For this reason, chelation of the copper comprising thecopper film MT due to the anodic oxidation can be efficiently carriedout.

Further, the magnitude of the current i₂ changes according to the sizeof the gap δ_(b) and the gap δ_(w), therefore, as mentioned above, byadjusting the size of the gap δ_(b) and the gap δ_(w) by controlling theposition of the polishing tool 11 in the Z-axial direction by thecontroller 55, the current i₂ can be made constant. The size of the gapδ_(w) can be adjusted by controlling the Z-axis servo motor 31 by usingthe current value signal 62 s as a feedback signal so that theelectrolytic current obtained from the current value signal 62 s, thatis, the current i₂, becomes constant.

Further, the positioning precision of the polishing apparatus in theZ-axial direction is a sufficiently high resolution of 0.1 μm. Inaddition, the main shaft 13 a is inclined with respect to the mainsurface of the wafer W at a fine angle, so the effective contact area isalways maintained constant, therefore if the value of the electrolyticcurrent is controlled constant, the current density can be made alwaysconstant and also the amount of chelation of the copper film due to theanodic oxidation can be made always constant.

As described above, the polishing apparatus having the aboveconfiguration is provided with an electrolytic polishing function forforming a chelating film by anodic oxidation and removing the same onthe surface of the copper film MT formed on the wafer W by theelectrolytic action by the electrolytic solution EL.

Further, the polishing apparatus having the above configuration isprovided with a chemical mechanical polishing function of the usual CMPapparatus by the polishing tool 11 and the slurry SL in addition to thiselectrolytic polishing function, so the wafer W can also be polished bythe combined action of the electrolytic polishing function and chemicalmechanical polishing (hereinafter referred to as electrolytic compositepolishing).

Further, the polishing apparatus having the above configuration is alsoable to perform the polishing by the combined action of the mechanicalpolishing of the polishing surface 11 a of the polishing tool 11 and theelectrolytic polishing function without the use of the slurry SL.

According to the polishing apparatus according to the presentembodiment, because the copper film can be polished by the combinedaction of the electrolytic polishing and the chemical mechanicalpolishing, the copper film can be removed with a much higher efficiencyin comparison with a polishing apparatus using only chemical mechanicalpolishing or mechanical polishing. For the copper film, a high polishingrate can be obtained, therefore it becomes possible to keep a lowpolishing pressure F of the polishing tool 11 on the wafer W incomparison with a polishing apparatus using only chemical mechanicalpolishing or mechanical polishing and the occurrence of dishing anderosion can be suppressed.

Further, in using a slurry in the chemical mechanical polishing of therelated art, if a slurry containing alumina particles or the like isused, after the polishing, the alumina particles may remain on thecopper surface without wear or may even be buried in the surface. By thepolishing apparatus according to the present embodiment, however, sincethe chelate film existing on the surface has a very low mechanicalstrength, it can be removed effectively even by only mechanicalpolishing using an electrolytic solution including a chelating agent notcontaining a polishing abrasive, so particles and slurry can beprevented from remaining on the wafer surface.

Further, the positioning precision of the polishing apparatus in theZ-axial direction is a sufficiently high resolution of 0.1 μm, inaddition, the main shaft 13 a is inclined with respect to the mainsurface of the wafer W at a fine angle, so the effective contact area isalways maintained constant, therefore if the value of the electrolyticcurrent is controlled constant, the current density can be made alwaysconstant and also the amount of chelation of the copper film due to theanodic oxidation can be made always constant.

In the above embodiment, the absolute value of the amount of polishingof the copper film can be controlled by the cumulative amount of theelectrolytic current and the time by which the polishing tool 11 passesover the wafer W.

Modification 1

FIG. 13 is a schematic view of a first modification of a polishingapparatus according to the present invention.

In the polishing apparatus according to the embodiment mentioned above,the current was conducted to the surface of the wafer W by theconductive plate 23 provided with the conductive polishing tool and thescrub member 24.

As shown in FIG. 13, it is also possible to give the wheel-likepolishing tool 311 conductivity in the same way as the case of theaforethe polishing apparatus and to give conductivity to a wafer table342 for chucking and rotating the wafer W. Power is supplied to thepolishing tool 311 by a configuration similar to that of theembodiments.

In this case, in supplying current to the wafer table 342, electrolyticcurrent can be supplied by providing a rotary joint 316 below the wafertable 342 and constantly maintaining the flow of current to the wafertable 342 rotating by the rotary joint 316.

Modification 2

FIG. 14 is a schematic view of a second modification of a polishingapparatus according to the present invention.

A wafer table 442 for chucking and rotating the wafer W holds the waferW by a retainer ring 410 provided on the periphery of the wafer W.

Conductivity is imparted to a polishing tool 411, conductivity isimparted to the retainer ring 410, and power is supplied to thepolishing tool 411 by a configuration similar to that of the embodimentsmentioned above.

Further, the retainer ring 410 covers up to the barrier layer portionformed on the wafer W and supplies current. Further, the retainer ring410 is supplied with power through a rotary joint 416 provided below thewafer table 442.

Note that by making the amount of inclination of the polishing tool 411larger so that a gap more than the thickness of the retainer ring 410can be maintained at the edge portion even if the polishing tool 411contacts the wafer W, interference between the polishing tool 411 andthe retainer ring 410 can be prevented.

Modification 3

FIG. 15 is a schematic view of a third modification of a polishingapparatus according to the present invention.

The polishing apparatus shown in FIG. 15 is obtained by adding theelectrolytic polishing function of the present invention to the CMPapparatus of the related art. It flattens the surface of the wafer W bybringing the entire surface of the wafer W chucked by a wafer chuck 207into contact with the polishing surface of the polishing tool comprisedof a plate 201 to which a polishing pad (polishing fabric) 202 isadhered while rotating the wafer W.

Anode electrodes 204 and cathode electrodes 203 are alternately radiallyarranged on the polishing pad 202. Further, the anode electrodes 204 andthe cathode electrodes 203 are electrically insulated by an insulator206, and the anode electrodes 204 and the cathode electrodes 203 aresupplied with the current from the plate 201 side. The polishing pad 202is constituted by these anode electrodes 204, cathode electrodes 203,and insulator 206.

The wafer chuck 207 is formed by the insulation material.

This polishing apparatus is provided with a feeder 208 for feeding theelectrolytic solution EL and the slurry SL to the surface of thepolishing pad 202, whereby electrolytic composite polishing combiningelectrolytic polishing and chemical mechanical polishing becomespossible.

Here, FIG. 16 is a view for explaining the electrolytic compositepolishing operation (polishing method) by the polishing apparatus havingthe above configuration. Note that, it is assumed that for example acopper film 210 is formed on the surface of the wafer W.

As shown in FIG. 16, DC voltage is applied between the anode electrodes204 and the cathode electrodes 203 in the state where the electrolyticsolution EL and the slurry SL are interposed between the copper film 210formed on the surface of the wafer W and the polishing surface of thepolishing pad 202, during the electrolytic composite polishing. Thecurrent i passes through the electrolytic solution EL from the anodeelectrode 204, is transmitted in the copper film 210, and passes throughthe electrolytic solution EL again to flow to the cathode electrode 203.

At this time, near the interior of the circle G shown in FIG. 16, achelating film is formed on the surface of the copper film 210 due toanodic oxidation. This chelating film is removed by the mechanicalremoval action due to the polishing pad 202 and the slurry SL, andtherefore the copper film is flattened.

By employing such a configuration, effects similar to those by thepolishing apparatus according to the embodiments described above areexhibited.

Note that the arrangement of the anode electrodes and the cathodeelectrodes provided on the polishing pad is not limited to theconfiguration of FIG. 15. For example, as shown in FIG. 17, it is alsopossible to employ a polishing pad 221 in which a plurality of linearanode electrodes 222 are vertically and laterally aligned at equalintervals, a cathode electrode 223 is arranged in each rectangularregion surrounded by the anode electrodes 222, and the anode electrodes222 and the cathode electrodes 223 are electrically insulated by aninsulator 224.

The polishing apparatus according to the present invention is notlimited to the above embodiments. Numerous modifications could be madethereto without departing from the basic concept and scope of theinvention in, for example, the materials comprising the apparatus,methods for supplying a current to a wafer, and so on.

Further, for example, as shown in FIG. 18, it is also possible to employa polishing pad 241 in which annular anode electrodes 242 having radiidifferent from each other are arranged in concentric circles, cathodeelectrodes 243 are arranged in the annular regions formed between theanode electrodes 242, and the anode electrodes 242 and the cathodeelectrodes 243 are electrically insulated by an insulator 244.

Second Embodiment

FIG. 19 is a schematic view of the configuration of a polishingapparatus according to a second embodiment of the present invention. Thepolishing apparatus according to the present embodiment comprises a tank501 filled with a predetermined amount of electrolytic solution EL, awafer holding means 530 and an electrode plate 510 arranged in theelectrolytic solution EL in the tank, a jet pump 520 (flowing means) forsucking the electrolytic solution EL in the tank using a tube 522 andejecting the same as a jet using a tube 521, a power supply 561(electrolytic current supplying means) for applying a voltage using theelectrode plate 510 as a cathode and a wafer as an anode, an ammeter562, a controller 555, and a control panel 556.

The holding means 530 comprises a first holding member 531 and a secondholding member 532 having conductivity and for holding a wafer and aZ-axis positioning mechanism fixed to a not illustrated column and forfixing the first holding member and the second member to specificpositions. The second holding member positioned below the wafer has acircular aperture at the portion 532 a.

The electrode plate 510 is arranged parallel with the wafer in theelectrolytic solution EL and is made of for example oxygen-free copperor the like.

The electrolytic solution EL for example contains a chelating agent forchelating copper. Other additives may also be included. As the chelatingagent, use is made of quinaldine acid, glycin, citric acid, oxalic acid,or propionic acid. The additives may include copper sulfate for reducingthe voltage applied between the wafer and the electrode plate 510.

The electrolytic power supply 561 (electrolytic current supplying means)is not a constant voltage power supply for continuously outputting aconstant voltage. It is preferable to use a power supply outputting avoltage pulse at a constant period. For example, the voltages applied bythe electrolytic power supply 561 are DC pulsed voltages with a highvoltage and low voltage repeated every five seconds (for example,voltage 30 to 40V, current 2.2A, and depending on the voltage toleranceof a semiconductor element, may also be set for example 10 to 20V).

The above DC pulsed power supply is preferably capable of selecting avoltage and pulse width able to most effectively remove a copper film byadjusting a distance d between the wafer and the electrode plate 510 orothers.

If the distance between the electrode plate 510 and the wafer is tosmall, the flushing action of the electrolytic solution between theelectrode plate 510 and the wafer does not function sufficiently.Preferably, the distance d is set larger than a specific value accordingto the setting of the above voltage.

The electrolytic power supply 561 is provided with an ammeter 562 as acurrent detecting means of the present invention. This ammeter 562 isprovided to monitor the electrolytic current flowing to the electrolyticpower supply 561 and outputs the monitored current value signal 562 s tothe controller 555.

Further, the controller 555 receives as input a current value signal 562s from the ammeter 562 of the electrolytic power supply 561. Thecontroller 555 is able to control the operation of the polishingapparatus based on the current value signal 562 s. Specifically, itcontrols the operation of the polishing apparatus so as to stop thepolishing based on the current value specified by the current valuesignal 562 s.

A control panel 556 connected to the controller 555 is used forinputting a variety of data by an operator or displaying the monitoredcurrent value signal 562 s.

According to the polishing apparatus configuration described above, asthe polishing apparatus according to the first embodiment, for example,in a case where an uneven copper film is formed on the surface of awafer, by applying a voltage using the wafer as an anode, the surface ofthe copper film on the wafer is oxidized by the anodic oxidation. Theoxidized copper film is chelated by the chelating agent in theelectrolytic solution EL. Because the mechanical strength of the chelatefilm is very low, the projecting portions of the chelate film areremoved by the flushing action of the electrolytic solution from thetube 521 of the jet pump 520, whereby the copper film is flattened.

Further, by monitoring the electrolytic current, the polishing processcan be controlled, so it becomes possible to correctly grasp the stateof progress of the polishing process.

According to the polishing apparatus according to the presentembodiment, since the copper film can be flattened by removing thechelate film of a very low mechanical strength, the copper film can beremoved with a much higher efficiency in comparison with a polishingapparatus using only chemical mechanical polishing or mechanicalpolishing.

Since a strong pushing force as in a polishing apparatus is notnecessary, the damage to the interlayer insulation film below the copperfilm can be suppressed very small and occurrence of dishing, erosion,etc. can be suppressed. Because there is no high pressure applied to theinsulation film below the copper film, as the insulation film, use maybe made of a low dielectric constant material having a mechanicalstrength lower than silicon dioxide using TEOS as a stock material.

Further, as a polishing apparatus, because the hardware configuration issimple, reduction of its size can be easily realized, maintenance iseasy, and the operation rate can be improved.

Further, in the chemical mechanical polishing of the related art, whenusing a slurry containing alumina particles etc., the alumina particlesmay remain on the copper film surface without wear after polishing, orthey may be buried in the surface of the copper. In the polishing methodof the present invention, however, these problems do not happen.

The present invention is not limited to the above embodiments. Numerousmodifications could be made thereto without departing from the basicconcept and scope of the invention in for example the configuration ofthe jet pump, type of the electrode plate, configuration of theapparatus holding a wafer in the tank, and so on.

Third Embodiment

FIG. 20 is a schematic view of the configuration of a polishingapparatus according to a third embodiment of the present invention. Thepolishing apparatus according to the present embodiment comprises avibration applying means including a pulse generator 640, an amplifier641, and an oscillator 643, a tank 601 filled with a predeterminedamount of electrolytic solution EL, a wafer holding means 630 and anelectrode plate 610 arranged in the electrolytic solution EL in thetank, a power supply 661 (electrolytic current supplying means) forapplying a voltage using the electrode plate 610 as a cathode and awafer as an anode, an ammeter 662, a controller 655, and a control panel656.

The holding means 630 comprises a first holding member 631 for holdingthe electrode plate to be parallel with the wafer W, a second holdingmember 632 and a third holding member 633 for pressing and fixing thewafer between them, and a fourth holding member 634 with one endattached to the second holding member 632 and the other end to theoscillator 643.

The second holding member 632 is made of a conductive material andfunctions to conduct a current through the wafer serving as an anode.Further, the second holding member 632 has an aperture portion 632 a forexposing the surface of the wafer to the electrode plate 610.

The electrolytic solution EL for example contains a chelating agent forchelating copper. Other additives may also be included. As the chelatingagent, use is made of quinaldine acid, glycin, citric acid, oxalic acid,or propionic acid. The additives may include copper sulfate for reducingthe voltage applied between the wafer and the electrode plate 610.

The electrode plate 610 is arranged parallel with the wafer in theelectrolytic solution EL and is made of for example oxygen-free copperor the like.

The electrolytic power supply 661 (electrolytic current supplying means)is not a constant voltage power supply for continuously outputting aconstant voltage. It is preferable to use a power supply outputting avoltage pulse at a constant period. For example, the voltages applied bythe electrolytic power supply 661 are DC pulsed voltages with a highvoltage and low voltage repeated every five seconds (for example,voltage 30 to 40V, current 2.2A, and depending on the voltage toleranceof a semiconductor element, may also be set for example 10 to 20V).

The above DC pulsed power supply is preferably capable of selecting avoltage and pulse width able to most effectively remove a copper film byadjusting a distance d between the wafer and the electrode plate 610etc.

If the distance between the electrode plate 610 and the wafer is toosmall, the flowing action of the electrolytic solution between theelectrode plate 610 and the wafer does not function sufficiently.Preferably, the distance d is set larger than a specific value accordingto the setting of the above voltage.

The electrolytic power supply 661 is provided with an ammeter 662 as acurrent detecting means of the present invention. This ammeter 662 isprovided to monitor the electrolytic current flowing to the electrolyticpower supply 661 and outputs the monitored current value signal 662 s tothe controller 655.

Further, the controller 655 receives as input a current value signal 662s from the ammeter 662 of the electrolytic power supply 661. Thecontroller 655 is able to control the operation of the polishingapparatus based on the current value signal 662 s. Specifically, itcontrols the operation of the polishing apparatus so as to stop thepolishing based on the current value specified by the current valuesignal 662 s.

A control panel 656 connected to the controller 655 is used forinputting a variety of data by an operator or displaying the monitoredcurrent value signal 662 s.

According to the polishing apparatus configuration described above, asthe polishing apparatus according to the first embodiment, for example,in a case where an uneven copper film is formed on the surface of awafer W, by applying a voltage using the wafer as an anode, the surfaceof the copper film on the wafer is oxidized by the anodic oxidation. Theoxidized copper film is chelated by a chelating agent in theelectrolytic solution EL. Because the mechanical strength of the chelatefilm is very low, the projecting portions of the chelate film areremoved by vibration of the wafer applied by the oscillator 643, wherebythe copper film is flattened.

Further, by monitoring the electrolytic current, the polishing processcan be controlled, so it becomes possible to correctly grasp the stateof progress of the polishing process.

According to the polishing apparatus according to the presentembodiment, since the copper film can be flattened by removing thechelate film of a very low mechanical strength, the copper film can beremoved with a much higher efficiency in comparison with a polishingapparatus using only chemical mechanical polishing or mechanicalpolishing.

Since a strong pressing force as used in a polishing apparatus is notnecessary, the damage to the interlayer insulation film below the copperfilm can be suppressed very small, and occurrence of dishing, erosion,etc. can be suppressed. Because there is no high pressure applied to theinsulation film below the copper film, as the insulation film, use maybe made of a low dielectric constant material having a mechanicalstrength lower than silicon dioxide using TEOS as a stock material.

Further, as a polishing apparatus, because the hardware configuration issimple, reduction of its size can be easily realized, maintenance iseasy, and the operation rate can be improved.

Further, in the chemical mechanical polishing of the related art, whenusing a slurry containing alumina particles etc., the alumina particlesmay remain on the copper film surface without wear after polishing ormay be buried in the surface of the copper. In the polishing method ofthe present invention, however, these problems do not happen.

The present invention is not limited to the above embodiments. Numerousmodifications could be made thereto without departing from the basicconcept and scope of the invention in for example the configurations ofthe oscillator and the amplifier, type of the electrode plate,configuration of the apparatus holding a wafer in the tank, and so on.

Fourth Embodiment

FIG. 21 is a view of the configuration of the principal portion of apolishing apparatus according to the present invention.

The basic configuration is the same as the first embodiment, but in thepresent embodiment, a polishing tool is not used. Instead, a metal filmon a wafer is removed by a wiping member 24 a.

Accordingly, for simplicity, only parts different from the firstembodiment are explained.

The wiping member 24 a, for example, is made of polyvinyl acetal (PVA),urethane foam, Teflon foam, Teflon nonwoven fabric, or the like. Astheir electric characteristics, they need to be insulators that do notconduct electricity or ions. For this, they are formed like fibers.Accordingly, an electrolytic solution can seep through the air holes inthe fiber-like wiping member and fill the space between an electrode 22and a wafer W.

The wiping member 24 a requires certain strength for it and the surfaceof the wafer W to be pressed to remove a metal film on the surface ofthe wafer.

For example, along with an elastic strength for tolerating 20 to 100g/cm² pressure for wiping off only projecting portions of a metal filmon the surface of a wafer W, a soft strength not causing scratches isrequired.

For example, an elastoplastic material can be used for the wiping member24.

Further, the electrode 23, for example, is preferably provided with anair hole for releasing the gas produced on the polished surface due toan electrolytic action of the metal film on the surface of the wafer W.The air hole is provided also for preventing disadvantages resultingfrom the non-uniformity of the electrolytic action between the electrode23 and the wafer W caused by the gas.

Further, the electrode 23 may be provided to be able to be driven torotate. As a result, the gas produced on the polished surface due toelectrolytic action can be released from between the wafer W and theelectrode 23 by the rotation of the electrode 23.

Further, the electrode 23 may be divided into several regions, wherebythe electrolytic action to the polished surface can be selectivelycarried out in individual regions.

The electrolytic power supply 61, as the first embodiment, applies apredetermined pulsed voltage between the previously described rotaryjoint 16 and a conductive brush 710 contacting the wafer.

Here, in the present embodiment, the voltage is applied in a reversedirection, therefore, the conductive brush 710 and electrode 23 becomethe anode and cathode, respectively. In addition to the configuration ofapplying voltage by contacting the metal film on the surface of a waferW using the conductive brush 710 as shown here, a configuration may alsobe employed which is provided with an electrode capable of being broughtinto proximity with the metal film on the surface of the wafer W forapplying a voltage.

The conductive brush 710 conducts a current to the wafer from theelectrolytic power supply 61 contacting the surface of the wafer.Therefore, the current supplied from the electrolytic power supply 61flows from the conductive brush 710 to the metal film on the surface ofthe wafer W and to the electrode 22 through the electrolytic solution.

The operation of the above polishing apparatus is explained below.

First, the wafer W is chucked on the wafer table 42, and the wafer table42 is driven to rotate the wafer W at a predetermined speed.

The wafer table 42 is moved in the X-axial direction, the wiping member24 a is positioned at a predetermined position above the wafer W, andthe wiping member 24 a is rotated at a predetermined speed. For example,the wiping member 24 a rotates at 100 rpm.

From this state, when the slurry SL and the electrolytic solution EL arefed to the feed nozzle 20 a in the conductive shaft 20 from the slurryfeeder 71 and the electrolytic solution feeder 81, the slurry SL and theelectrolyte EL are fed from the entire surface of the wiping member 24a.

Then, the electrolytic power supply 61 is activated, a positive voltageis applied to the metal film on the surface of the wafer through theconductive brush 27, and a negative voltage is applied to the electrode23 through the rotary joint 16.

As a result, a positive voltage is applied directly to the metal film onthe surface of the wafer through the conductive brush 27, and a currentis conducted to the electrode 22 through the electrolytic solution.

Therefore, a current can be supplied through the electrolytic solutionusing the metal film below the wiping member 24 a as the anode. Themetal film is oxidized by the anodic oxidation caused by an electrolyticaction of the electrolytic solution and is chelated by a chelating agentin the electrolytic solution.

In the above state, high pressure air is fed to the cylinder device 15to move the piston rod 15 b downward, and the bottom surface of thewiping member 24 a is brought into contact with the surface of the waferW.

The wafer table 42 is moved in the X-axial direction with apredetermined speed pattern from this state, whereby the entire surfaceof the wafer W is uniformly wiped.

As shown above, a polishing apparatus employing the above configurationis able to produce a chelating film described above by the anodicoxidation on the surface of a metal film formed on a wafer W and removeit.

According to the polishing apparatus of the present embodiment, effectssimilar to the one according to the first embodiment are exhibited.

Further, in the polishing apparatus according to the present embodiment,because a polishing tool is not used and the step difference of a metalfilm on the surface of a wafer can be reduced by only wiping using thewiping member 24 a, the pressure against the wafer can be furtherreduced lower than in the polishing apparatus according to the firstembodiment.

In the present embodiment, rotation of the wiping member was shown anexample of the wiping method, but the wiping member can also be movedrelative to the wafer W. For example, a wiping member can be moved byproviding a horizontal moving means. In the case of wiping by horizontalmovement, it is preferable to set the speed of the horizontal movementbelow about 15 m/min in order to prevent the electrolytic solution fromspraying out.

Preferably, the temperature of the electrolytic solution is adjustedbelow 80 degree or so in order to accelerate the anodic oxidation.

Further, the electrolytic solution fed to the surface of the polishingobject can be held by surface tension.

As described previously, there is no limit to the polishing object.

Next, further embodiments of the method of production and method ofpolishing of a semiconductor device of the present invention and apolishing apparatus using the same will be explained with reference tothe drawings.

Fifth Embodiment

FIG. 22A and FIG. 22B compare the amount of copper film removed per unittime when removing a copper film on the surface of a wafer by chelationby anodic oxidation employing the polishing apparatus according to thethird embodiment of the present invention and the amount of copper filmremoved per unit time when removing a copper film on the surface of awafer by oxidation with hydrogen peroxide (H₂O₂) of a predeterminedconcentration added to the electrolytic solution EL as an oxidant of thecopper film on the surface of a wafer, without applying a voltage on thewafer W, employing the polishing apparatus according to the thirdembodiment of the present invention.

FIG. 22A shows removal rates when removing copper by adding an oxidantwithout applying a voltage to oxidize the copper and then chelating it.The amount of copper film removed per unit time (removal rate) wasmeasured using a quinaldine acid solution as the electrolytic solutionat concentrations of hydrogen peroxide (H₂O₂) of 0%, 4.5%, 8%, 10.7%,respectively. Note that the volume of the electrolytic solution was 150ml.

Further, FIG. 22B shows the removal rate when copper was removed usingthe polishing-apparatus according to the third embodiment of the presentinvention. The amount of copper film removed per unit time (removalrate) was measured when using 150 ml quinaldine acid solution not addedwith hydrogen peroxide (H₂O₂) as the electrolytic solution EL and when avoltage was applied so that a current of 2.2A flows to the electrodeplate 610 and the wafer through the electrolytic solution EL.

When using the hydrogen peroxide for an oxidant, aqueous copper ions([Cu(OH)₄]²⁻) are formed. The aqueous copper ions are chelated by thechelating agent in the electrolytic solution EL. For example, when thechelating agent is a quinaldine acid, a chelate film of the chemicalformula (6) is formed. When glycin is used, a chelate film of thechemical formula (7) is formed.

The other experimental conditions include using an eight-inch wafer, a25 nm thick Ta as the barrier metal, a 1200 nm-thick TEOS (tetraethylorthosilicate) film for the interlayer insulation film, and a 1600 nmthick copper film.

In FIG. 22, it is clear that the amount of copper film removed per unittime increased because the amount of the chelate film produced by copperfilm oxidation increases with an increased amount of the hydrogenperoxide serving as an oxidant, but when using the polishing method bythe polishing apparatus according to the third embodiment of the presentinvention, without adding the hydrogen peroxide and by only the anodicoxidation caused by current conducting to produce a chelate film, it isshown the removal rate is raised greatly in comparison with that causedby an oxidant.

Sixth Embodiment

FIG. 23 is a view of the measured thickness of a copper film after achelate film is removed when a current of 2.2A is supplied for 30seconds each time using a copper film for an anode to remove the chelatefilm.

The measurements; were made at 21 points on an eight-inch wafer with thewafer divided into 21 parts along a diameter direction. The first andthe 21st points were 6 mm apart from the edge of the wafer,respectively.

In addition, a quinaldine acid solution was used for an electrolyticsolution. The thickness of the copper film was 2000 nm. A 25 nm thick Tawas used for the barrier metal. Use was made of a wafer having a 1200 nmthick TEOS film used for the interlayer insulation film below thebarrier metal.

In FIG. 23, numbers 0, 1, 2, 3, 4, 5 along the horizontal axis indicatethe times of the 30-second conduction of a 2.2A current. Therefore, 0means no current is conducted, 1 means conduction of a 2.2A current for30 seconds, 2 for total 60 seconds, 3 for a total 9.0 seconds, 4 for atotal 120 seconds, and 5 for a total 150 seconds.

The vertical axis indicates the thickness (nm) of the residual copper onthe surface of the wafer after the copper removing process by currentconduction.

The measurements were repeated several times under the same conditions.

It is shown from the results that each time a current is conducted for aspecific time period, the thickness of the residual copper after thecopper removing process decreases corresponding to the time period ofcurrent conduction. The average removal rate was 202.68 nm per minute.

Seventh Embodiment

FIG. 24 shows the results of similar measurements as those in FIG. 23made at 21 points on an eight-inch wafer with the wafer divided into 21parts along a diameter direction.

The current and the conduction time are the same as the sixthembodiment. Measurements were made of the thickness of the residualcopper after the process of removing the copper film in a case where 30second conduction of a 2.2A current was repeated several times.

Other conditions such as the wafer in use, the type of the electrolyticsolution, etc. are the same as the second embodiment.

In FIG. 24, the numbers 1 to 21 along the horizontal axis represent theaforethe positions on the wafer, while the vertical axis represents thethickness (nm) of the residual copper after the removal. Specifically,A, B, C, D, E, F represent the thickness (nm) of the residual copperafter the removal after conduction of a 2.2A current for a total of 0second, 30 seconds, 60 seconds, 90 seconds, 120 seconds, and 150 secondsrespectively at each and every point described above.

According to the present embodiment, the thickness of the copper film ateach and every point decreases approximately linearly depending on theproduct of the current and the time. Note that the smaller thicknessesof the copper film at the first and the 21st point are due to theplating characteristics during the preceding step for forming the copperfilm and are irrelevant to the polishing method of the presentinvention.

Summarizing the effects of the present invention, according to themethod for producing a semiconductor device using the polishing methodof the present invention, since the copper film is polished by thecomposite actions of mechanical polishing and electrolytic polishing, incomparison with the case of the flattening of the copper film bymechanical polishing, very highly efficient selective removal andflattening of the projecting portions of the copper film becomepossible.

Further, according to the method for producing a semiconductor deviceusing the polishing method of the present invention, since a sufficientpolishing rate is obtained even with a relatively low polishingpressure, the occurrence of scratches, dishing, or erosion in thepolished metal film can be suppressed. In addition, since damage to aninterlayer insulation film below a copper film can be suppressed, evenin the case where an organic low dielectric constant film or porous lowdielectric constant insulation film having a relatively low mechanicalstrength is used as the interlayer insulation film in order to reducethe dielectric constant from the viewpoint of lowering the powerconsumption and increasing the speed of the semiconductor device, theinvention can be easily applied.

Further, according to the method for producing a semiconductor deviceusing the polishing method of the present invention, by monitoring theelectrolytic current, the polishing process can be controlled, so itbecomes possible to correctly grasp the state of progress of thepolishing process.

According to the polishing apparatus of the present invention, since themetal film is polished by the composite actions of mechanical polishingand electrolytic polishing, in comparison with the case of theflattening of the metal film by mechanical polishing, very highlyefficient selective removal and flattening of the projecting portions ofthe metal film become possible.

Further, according to the polishing apparatus of the present invention,since a sufficient polishing rate is obtained even with a relatively lowpolishing pressure, the occurrence of scratches, dishing, or erosion inthe polished metal film can be suppressed. In addition, since damage toan interlayer insulation film below a copper film can be suppressed,even in the case where an organic low dielectric constant film or porouslow dielectric constant insulation film having a relatively lowmechanical strength is used as the interlayer insulation film in orderto reduce the dielectric constant from the viewpoint of lowering thepower consumption and increasing the speed of the semiconductor device,the invention can be easily applied.

Further, according to the polishing apparatus of the present invention,by monitoring the electrolytic current, the polishing process can becontrolled, so it becomes possible to correctly grasp the state ofprogress of the polishing process.

Further, according to the polishing apparatus of the present invention,because the configuration of the apparatus is simple, reduction of itssize can be easily realized, maintenance is easy, and the operation ratecan be improved.

While the invention has been described with reference to specificembodiments chosen for purpose of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

1. A polishing apparatus for polishing an object having a metal film onthe surface to be polished, comprising: a holding means for holding theobject having the surface to be polished; a wiper for wiping the surfaceof the object; an electrolytic solution feeding means for feeding anelectrolytic solution on the surface of the object; a facing electrodearranged at a position facing the surface of the object; and a currentsupplying means for supplying a current between the surface of theobject and the facing electrode, wherein said electrolytic solutionfeeding means has a seepage member made of a material capable ofallowing an electrolytic solution to seep out at the end thereof andfeeds an electrolytic solution onto the surface of the object throughthe seepage member, and further comprising a temperature adjusting meansfor adjusting the temperature of the electrolytic solution fed by saidelectrolytic solution feeding means.
 2. A polishing apparatus as setforth in claim 1, wherein said metal film comprises an interconnectionmetal film.
 3. A polishing apparatus as set forth in claim 2, whereinsaid metal film comprises at least one of copper, aluminum, tungsten,gold, and silver, or an alloy of them, or an oxide or nitride of any ofthem.
 4. A polishing apparatus as set forth in claim 1, wherein saidwiper is made of an elastic material.
 5. A polishing apparatus as setforth in claim 1, wherein said wiper is provided with an air hole.
 6. Apolishing apparatus as set forth in claim 1, wherein said electrolyticsolution feeding means feeds an electrolytic solution so that theelectrolytic solution is contained on the surface of the polishedobject.
 7. A polishing apparatus as set forth in claim 1, furthercomprising a tank formed so as to surround the periphery of said objectand for containing the electrolytic solution fed by said electrolyticsolution feeding means.
 8. A polishing apparatus as set forth in claim1, wherein said electrolytic solution feeding means feeds anelectrolytic solution comprising an electrolyte and an additive.
 9. Apolishing apparatus as set forth in claim 8, wherein said additivehaving at least one of a brightener, a chelating agent, and copper ions.10. A polishing apparatus as set forth in claim 8, wherein saidelectrolytic solution having a polishing abrasive.
 11. A polishingapparatus as set forth in claim 1, wherein said facing electrodecomprises a metal material at least as precious as the metal film on thesurface on the object.
 12. A polishing apparatus as set forth in claim1, wherein said facing electrode comprises an air hole.
 13. A polishingapparatus as set forth in claim 1, wherein said facing electrode can bedriven to rotate.
 14. A polishing apparatus as set forth in claim 1,wherein said facing electrode is divided into several regions.
 15. Apolishing apparatus as set forth in claim 1, further comprising acontact electrode for guiding a current form said current supplyingmeans to a metal film on the surface of the object.
 16. A polishingapparatus as set forth in claim 1, further comprising an electrodecapable of being located selectively in proximity to the surface of saidobject and for guiding a current from said current supplying means to ametal film on the surface of the object.
 17. A polishing apparatus asset forth in claim 1, wherein said current supplying means supplies acurrent by applying a periodical pulse-like voltage between the surfaceof said object and said facing electrode.
 18. A polishing apparatus asset forth in claim 17, wherein said current supplying means supplies acurrent by applying a periodical pulse-like voltage having arectangular, sinusoidal, sawtooth, or PAM waveform between the surfaceof said object and said facing electrode.
 19. A polishing apparatus asset forth in claim 1, wherein said current supplying means is able tochange a current flowing between the surface of said object and saidfacing electrode at least at the beginning and end of the polishing. 20.A polishing apparatus as set forth in claim 1, wherein said temperatureadjusting means adjusts the temperature of the electrolytic solution tobelow 80° C.
 21. A polishing apparatus for polishing an object having ametal film on the surface to be polished, comprising: a holding meansfor holding the object having the surface to be polished; a wiper forwiping the surface of the object; a relative moving means for relativelymoving the surface of the object and the wiper; an electrolytic solutionfeeding means for feeding an electrolytic solution on the surface of theobject; a facing electrode arranged at a position facing the surface ofthe object; and a current supplying means for supplying a currentbetween the surface of the object and the facing electrode, wherein saidrelative moving means presses said wiper against the surface of saidpolished object and horizontally moves the wiper on the surface of saidpolished object, wherein said relative moving means horizontally movessaid holding means in a surface parallel with the surface of said wiper,wherein said electrolytic solution feeding means has a seepage membermade of a material capable of allowing an electrolytic solution to seepout at the end thereof and feeds an electrolytic solution onto thesurface of the polished object through the seepage member, and furthercomprising a temperature adjusting means for adjusting the temperatureof the electrolytic solution fed by said electrolytic solution feedingmeans.
 22. A polishing apparatus as set forth in claim 21, wherein saidmetal film is an interconnection metal film.
 23. A polishing apparatusas set forth in claim 22, wherein said metal film comprises at least oneof copper, aluminum, tungsten, gold, and silver, or an alloy of them, oran oxide or nitride of any of them.
 24. A polishing apparatus as setforth in claim 21, wherein said relative moving means presses said wiperon the surface of polished object and rotates the wiper relative to apredetermined center axis of rotation.
 25. A polishing apparatus as setforth in claim 21, wherein said relative moving means rotates saidholding means relative to a predetermined center axis of rotation.
 26. Apolishing apparatus as set forth in claim 21, wherein said wiper is madeof an elastic material.
 27. A polishing apparatus as set forth in claim21, wherein said wiper is provided with an air hole.
 28. A polishingapparatus as set forth in claim 21, wherein said electrolytic solutionfeeding means feeds an electrolytic solution so that the electrolyticsolution is contained on the surface of the object.
 29. A polishingapparatus as set forth in claim 21, further comprising a tank formed soas to surround the periphery of said object and for containing theelectrolytic solution fed by said electrolytic solution feeding means.30. A polishing apparatus as set forth in claim 21, wherein saidelectrolytic solution feeding means feeds an electrolytic solutionincluding an electrolyte and an additive.
 31. A polishing apparatus asset forth in claim 30, wherein said additive having at least one of abrightener, a chelating agent, and copper ions.
 32. A polishingapparatus as set forth in claim 30, wherein said electrolytic solutionhaving a polishing abrasive.
 33. A polishing apparatus as set forth inclaim 21, wherein said facing electrode comprises a metal material atleast as precious as the metal film on the surface on the object.
 34. Apolishing apparatus as set forth in claim 21, wherein said facingelectrode comprises an air hole.
 35. A polishing apparatus as set forthin claim 21, wherein said facing electrode can be driven to rotate. 36.A polishing apparatus as set forth in claim 21, wherein said facingelectrode is divided into several regions.
 37. A polishing apparatus asset forth in claim 21, further comprising a contact electrode forguiding a current form said current supplying means to a metal film onthe surface of the object.
 38. A polishing apparatus as set forth inclaim 21, further comprising an electrode able to be brought intoproximity with the surface of said object and for guiding a current fromsaid current supplying means to a metal film on the surface of theobject.
 39. A polishing apparatus as set forth in claim 21, wherein saidcurrent supplying means supplies a current by applying a periodicalpulse-like voltage between the surface of said object and said facingelectrode.
 40. A polishing apparatus as set forth in claim 39, whereinsaid current supplying means supplies a current by applying a periodicalpulse-like voltage having a rectangular, sinusoidal, sawtooth, or PAMwaveform between the surface of said object and said facing electrode.41. A polishing apparatus as set forth in claim 21, wherein said currentsupplying means is able to change a current flowing between the surfaceof said object and said facing electrode at least at the beginning andend of polishing.
 42. A polishing apparatus as set forth in claim 21,wherein said temperature adjusting means adjusts the temperature of theelectrolytic solution to below 80° C.